The purpose of the research is to gain an understanding of the mechanism of self-assembly of neuronal microtubules and factors which control the formation and depolymerization of these structures. Experiments are designed to: To study kinetics and thermodynamics of the self-assembly process of pure tubulin including both the initiation and elongation processes. To examine the exact role of the associated proteins in the self-assembly reaction. To study the interaction of membranes and microtubules in vivo. To determine the role that divalent cations play in microtubule formation. To examine in more detail the interaction of GTP and colchicine with tubulin and microtubules. To determine the relative importance of various amino acid residues in the mechanism of reassembly.